Deviation correcting means for magnetic devices



June 22, 1948. F. D. BRADDON DEVIATION CORRECTNG MEANS FOR MAGNETICDEVICES Filed Jan. 22, 1943 3 Sheets-Sheet 1 INVENTOR FIG. 2.

FREDERICK D. BRADDON jMLw/M HIS TTQRNEY l June 22, 1948.

F. D. BRADDON 2,443,595 Y `DEVIATION CORRECTING MEANS FOR MAGNETICDEVICES Filed Jan. 22. 194s FIG. 3.

/l/lll/lllllllllllllllll 3 Sheets-Sheet l22 lllllllll/llllllllllll,

liminnr INVEN'TOR FREDERICK D. BRADDON ul'le 22,1948. F Q BRADDQN2,443,595

DEVIATION CORRECTING MEANS FOR MAGNETIC DEVICES Filed Jan. 22, 1943 3Sheets-Sheet 3 MAGNETIC DEVICE FIXED DEVIATION EFFECTS TEMPORARYDEVIATION t EFFECTS l RADIO RECEIVER TEMPORARY DEVIATIONy EFFECTS 2ELECTRIC PILOT .IvENToR FREDERICK D. BRADDON Patented June 22, 1948DEVIATION CORRECTING MEANS FOR MAGNETIC DEVICES vFrederick D. Braddon,Babylon, N. Y., asslgnor to The Sperry Corporation, a corporation ofDelaware Application January z2, uns, serial No. 473,264

(ci. '3s-225)` 3 Claims.

A further object of the invention is to facilitate ready adjustment ofthe deviation correcting means for a magnetic compass of the type whichmay or may not be located at a remote position on the dirigible craft inwhich it is employed.

One of the features of the invention resides in the provision of coilmeans situated in the vicinity of the sensitive element of the magneticdevice from which a controllable resultant corrective iiux eld may beobtained.

Another feature of the invention consists in provision of circuit meansfor controlling the respective deviation correcting coils for the xedsource of local effects and each of the individual temporary andtransient sources of such eiects.

A still further feature resides in the provision for making the circuitmeans correcting the compass for deviation due to a temporary localdeviation causing attraction automatically eiiec tive.

Other objects, features and structural details of the invention will beapparent' from the following description when read in relation to theacompanying drawings, wherein Fig. l is a perspective view of adirigible craft such as an airplane showing a magnetic compass system inwhich the present invention is incorporated.

Fig. 2 is a detail view, partly in vertical cross section showing one ofthe magnetic devices in which the present inventive concepts may beincluded.

Fig. 3 is a side elevation, with the casing in vertical section, showingthe invention adapted for use in a repeater compass controlling type ofmagnetic compass.

ment of the magnetic compass may be sta.-4

Fig. 7 is a further circuit diagramshowing a practical adaptation of theinvention in a craft oi' the character noted in Fig. 1 in which thecontrols for the respective deviation effects are situated in a singlecorrector panel.

In the form of the invention shown in Fig. 3, the magnetic compassinstrument is oi the direct reading type that may be located on theinstrument board panel l0 of a 'dirigible craft or airplane il, Fig. l..This instrument is generally similar in character to the type cimagnetic compass shown and described in U. S. Letters Patent No.2,300,404, issued November 3, 1042, to L. F. Carter and W. Anscott, withthe remote reading features of the therein disclosed instrumenteliminated. This instrument as shown in Fig. 2 includes a'casing i2 inthe front owhich is a window i3 through which a side reading compasscard ifi is visible to an observer. Card i@ is read in connection with asuitable vertical ex tending lnbber line provided in thepresent-construction by the forward portion o a bent rod it. Thesensitive element of the magnetic compass is provided by two spacedpermanent magnets, one of which is indicated at it, the same beingresponsive to the horizontal component of the earths magnetic eld. Themagnets are spaced in parallel relation by means of suitable mountingpieces il contained in the body oi' the compass card providing casingi8. Card casing I8 is mounted for pivotal movementv about a verticalaxis by means of shaft I Q which is supported in suitable upper andlower jewel posts in a vertical frame 2l). The rearward ends of the rodl5 are ilxed to the frame 20. It will be understood that the magnets i6,card housing Il with the side reading compass card thereon and the shafti9 move as a unit with respect to the frame 20.

Frame 20 and consequently the sensitive eiebilized by Vmeans of asuitable gyro vertical instrument as generally indicated at 22. In themanner shown morel in detail in the hereinbefore mentioned patent, theframe 20 is universally mounted by means of a bifurcated mem- Figs. 4and 5 are circuit diagrams illustrating the electrical connections forthe lelements constituting one form of the improved. magnetic compasscorrecting means. l l

Fig 6 is a view similar to Fig. 3 showing the invention adapted i'or usewith the sensitive element of a' iiux valve typeof magnetic compass, and

ber 23 that extends from and is :fixed to the gimbal ring of the gyrovertical. The extending arms of the member 23 have inwardly dis- -posedtrunnions, one of which is noted at 2l that journal in suitable bearings25 in the oppositely disposed legs of the frame 20. 'Iilt of the i'rame20 about the thus deilned athwartship axis of horizontal support of theframe with reference tothe craft is controlled by link 26. Similarlydicular relation.

the fore and aft horizontal axis of universal support of the frame isprovided by the bifurcated extension member 22 of the gimball ring ofthe gyro vertical instrument. The rotor bearing case and gimbal ringofthe gyro vertical instrument are respectively indicated at 21 and 2l.The gyro instrument is of conventional iorm and is employed herein tomaintain the sensitive element of the illustrated magnetic compass in a'horizontal plane with reference to the earth's surface.

The deviation correcting means shown in Fig.

2 consists of a plurality of coils that are mounted within the casing orcompass housing I2 with the y axes thereof arranged in fixed mutuallyperpen- In the form of the invention shown, coils of the Helmholtz" typeare em-A ployed. The coil arranged in coaxial relation with the fore andaft axis of universal support of compassframe 20 is indicated at III.The coil at right angles to the same is provided by two spaced parallelcoils 3|, only one of which is shown. Coils 3i are coaxial, in thisinstance. with the athwartship axis of universal mounting of the compassframe 20. lis shown, the coils may be connected to the inner wall of thecasing or housing i2.

The coils of the correcting means are positioned adjacent the magneticdevice or compass. and the respective axes thereof are arranged inspaced angular relation to one another in a horizontal plane, suchrelationship preferably y being as shown in the drawing.

In the form of the invention shown in Fig. 3, the magnetic compass isadapted for connection with a repeater compass which it controls, thesensitive element of the combination being located at a remote positionon craft il such as at the'end of the wing of the same. The housing orcasing of this instrument is indicated at 33 in Figs. 1 and 3. '.lheremay be one or a plurality of repeater compasses, one of the same be--ing indicated at 34 on the instrument board panel I0 of the craft. Acable connection Il is shown linking the controller and controlledinstrument which are described in detail in regard to the remote controlfeatures ot the aforementioned application. With reference to Fig. 3,the sensitive element of the magnetic compass shown therein comprises abar magnet 0I which is mounted on the upwardly extending shaft 31 of therotor of a selsyn" type transmitter whose .casing is indicated at Il.The transmitter and bar It are pendulously supported .within the housingIl by means of the gimbal ring 39 which also mounts the same foruniversal movement, the arrangement normally maintaining bar n inhorizontal position. The compensating or correcting means provided inthis instance include spaced pairs of coils oi -the Helmholtz type thatare arranged sub` stantially coaxial with the bar, as viewed in Fig. 3,about its fore and aft axis of universal support. Paired coils Il', onlyone of which ,is shown, are similar to coils 3i previously described. Inthis form of the invention a further pair of coils 4i may be employed,the same being coaxial with shaft 31, as viewed in Fig. 3, and beingalso mounted within the housing or casing Il in a iixed location on theinner wall of the housing.

The circuit shown in Fig. 4 may be employed in the forms of theinvention illustrated in both Figs. 2 and 3. As shown, a current sourceis lgenerally indicated at 42 which may be a battery,

the same providing a means for supplying the respective coils withenergy from a common source. To control the polarity of .the coils, acommon lead 43 is connected to a center tap position on the battery 42.Coil I0 or paired. series-connected coils 20' may be energized from thesource by way of lead 44 and potentiometer 41. 8imilarly,supply leads 45and 4l are respectively provided for the series-connected coils Il or Iiand for coils 4i. The energy supplied these respective coils iscontrolled by potentiometers 4l and 4l. The polarity and current in thereversible circuits thus provided may be ascertained by employing asuitable ammeter in the respective leads 44, 45 and 44. Such ammetersare respectively indicated at 15. 16 and 11. By adjusting the positionof the variable arm of the potentiometers to either side oi a balancedcentral position, the energy supplied the individual coils is controlledin such a manner as to obtain a resultant ilux ileld from the vcombinedcoils that is effective to correct the sensitive element of the magneticcompass in this instance against any deviation thereof due to fixeddeviation causing eilects. In accordance with the terminology employedherein, local ilxed deviation causing effects in the craft or airplanemay be considered to be a resultant defleeting magnetic ileld due to thecombined effect of al1 of the magnetic field radiating or attractingbodies tixedly incorporated in the structure of the craft. The same or asimilar separate circuit may be employed for correcting a magneticdevice of this character against deviation due to temporary sources ofattraction such as may be considered to be caused by releasable objectson the craft such as bombs or torpedoes. The potentiometers 41, 4l, 4lprovide a means for regulating the ilelds of the individual coilsemployed to obtain a resultant corrective flux ileld compensating thesensitive element of the magnetic compass against deviation thereof dueto the resultant -of such local and/or transient fixed deviation from are'lnotfv.- position is one of the primary advantages of the presentinvention. In the normal operation of a given craft, the potentiometers41, 48 or ,41. 4l and 4l may be adjusted as required upon change of thetemporary source of local attraction if the circuit is utilized in thisconnection. I'he invention also contemplates the utilization of theimproved deviation correcting means for also correcting the magneticcompass for transient deviation causing local eil'ects such as resultingfrom a radio transmitter or receiver,special electrical equipment. orother mitter 50 is employed for illustrative purposes in thisconnection.

The magnetic device responsive to the hori-V zontal component of theearths magnetic ileld employed in connection with the form oi theinvention shown in Fig. l6 is an earth inductor compass of the iluxvalve type such as specifically shown and described in the copendingapplication of Orland E. Esval, Robert S. Curry, Caesar F. Fragola andLennox F. Beach, Serial No. 414,422 filed October 10, 1941,v for Fluxvalve compass system, which became Patent No. 2,383,461, issued August28, 1945. The sensitivey element of the ux valve generally designated at52 is pendulously supported within a housing 3l on a universal mountingprovided by the gimbal ring 54, the output coils of the valve beingsituated in a horizontal plane withreference to the earth. Housing 33'is positioned as shown in Fig. 1 at a remote location from the repeatercompass 3| which is controlled thereby, it being understood that theoutput of the valve is fed by way of cable 35 to the repeater compass.The exciting its and output coils of the ux valve are respectivelyindicated at 55 and 56. The correcting coil means 61, 58 and 59, 6D. Acontrollable circuit means similar to that previously described isprovided for regulating the flow of energy to the coils 59 and B0, Fig.5, to correct the output of the ilux valve for change thereof due tolocal xed and temporary deviation causing effects. As shown in Fig. 5, asecond or auxiliary circuit means 'is provided to correct the output ofthe valve for deviation thereof due to operation of the radiotransmitter 56 or other transient local deviation causing attractionwhich itself' may be energized when a switch 68 in series with thebattery 42 is closed. The second circuit means includes, inthisinstance, the common lead 43, with the further leads 63 and 64 andpotentiometers 65 and 66, respectively. It will be understood that theresultant field set up by the electromagnetsinuences the sensitiveelement of the iiux valve so that the output thereof is changed orcorrected. A number of separate circuits, similar to the describedsecond circuit, for each of the transient sources of deviation causingdisturbances in the craft may be employed as hereinafter moreparticularly described. 'I'he compass or magnetic device is thuscompensated for the described type of disturbances through the singlecorrecting means. Once adjustment of the potentiometers 65 and 6 6 fora' particular or number of particular disturbing transient causes ofdeviation of the magnetic compass has been made, no further regulationmay be needed and the circuits are automatically effective to obtain theneeded correction from the compensating means upon closure of the switchto the particular or number of particular deviation causing electricalinstruments.

It will be understood that the correcting means may also be utilized inconnection with a compass of the rotary earth inductor type. Also, thecompensating coils, ii desired, may be constructed for direct mountingon the pendulous portion of the compass instrument shown in Figs. 3 and6 or on the stabilized frame 20 of the instrument vshown in Fig. 2 withequal effectiveness.

rector panel II situated at the instrument board panel of the craft. Inthis instance, three sources of transient deviation causing effects areillustrated, the same being radio transmitter Il, radio receiver!! andelectric pilot 83. The control panel Il includes ammeters and and anumber of paired potentiometers with common lead 88. The pair ofpotentiometers l1 and 8B are employed to correct the compass againstdeviation due to xed deviation effects. Once the settingof thesepotentiometers is made the same will remain ilxed. superimposed on thexed correcting signal are further signals resulting from five othercircuits in this instance, two of which compensate the compass forerrors due to temporary deviation causing effects. These last circuitsare controlled by the respective paired potentiometers Sii-96 and Si--SlIt for example, a separate deviation correcting circuit is provided foreach of the temporary causes ot deviation, when a change occurs and thecause of deviation is no longer present, the proper circuit is restoredto a balanced condition by adjustment of the potentiometers. This altersthe supply of current to the coil or correcting means to recorrect thecompass for the resulting change in the fixed and temporary deviationcausing effects.

The other individual currents provide additional control whereby thesupply of energyV tothe individual coils is regulated to correct thedevicel Iagainst deviation 'due to transient locai deviation causingeffects. 'Paired potentiometers 93--94 control the iiow of current tothe coils when the electric pilot @il is rendered eiective by closure ofthe switch 65. A further similar control circuit is provided for theradio receiver 82 which includes switch @t and the paired potentiometersSS-iil. Potentiometers-Ql--t are -provided for the control circuitrendered effective by closure of the switch 68 for the radio Vtrans-.mi-tter 56.

The operation of the circ-uit illustrated in Fig. 7 should be understoodfrom the following -brie description thereof. It will be noted thatthebattery lili is connected, under normal operating conditions, across thepotentiometers @l through 92 and therefore that the setting of thesepotentiometers continuously controls the magnitude and direction of theresultant eld produced by the magnetic device 66.' The voltages derivedtrom these potentiometers control the magnetic device to correct for xedor continuously existing deviation effects. Assuming, however, that theswitch 96 is closed, placing the radio receiver I2 in operation, thebattery will then be connected across the potentiometers SQ Iand ittherebyV impressing la voltage across both potentiometers. This circuitm'ay be traced from one side of the battery |01 through conductor |02,switch 96, and conductor |03 to the common connection |04 betweenpotentiometers 99 and H10. The other ends of these potentiometers areboth connected to conductor m5 which, in turn, -is connected to theother side of battery IUI. The vwipers of these potentiometers areadjusted to pick ofi a voltage therefrom of the correct magnitude Vandpolarity sense, when applied to the magnetic device I0, as'lto vary themagnitude or the direction, or both, of the ileld produced by themagnetic device, and this change will necessarily be of a fixed,4predetermined value only,

whereby to correct ior the deviation error otherwise caused by the radioreceiver on the magnetic compass. The wiper oi' potentiometer l0 isconnected to conductor I which .through ammeter I4 is connected with onecoil o! the magnetic device 80, and the wiper of potentiometer |00 isconnected through conductor |01 in a similar manner to another coil ofthe magnetic device. The common return lead 80 from lthe magnetic deviceis connected with jumper |00 which is connected between preferably themid-points of the two potenticmeters 99 and |00. It should be evidentfrom the foregoing that the circuit oi Fig. 7, so iar as it relates toone of the devices providingl .temporary deviation eilects, is quiteYsimilar to the circuit illustrated in Fig. 5. Adjustment of the wipersof these potentiometers will determine the polarity sense of thevoltages applied to the coils embodied in the magnetic device, and alsothe magnitudes thereof. Further, it will be observed that the switch 96functions as a common means for connecting and disconnecting the batterywith the potentiometers 99 and |00 with on-oi control of the temporarydeviation-causing apparatus. By operating the various switches 60, 95and 95, the respective poten-tiomete'rs associated therewith lwill berendered operative and inoperative to control the magnetic iielddeveloped by .the magnetic device 00.

It is to be understood that the term "magnetic compass as employed inthe appended claims isintended to include all devices which aresensitive to an external magnetic field such. for example, as compassescomprising ileld-sensitive magnetic needles or those ofthe flux valvetype which provide a'signal voltage output as an` indication of thedirection of an external tleld relative thereto. Y

Since many changes could be made in the above construction and manyapparently widely dii'-v ferent embodiments of this invention could .bemade without departing from the scope thereof, it is intended .that allmatter contained in the above descriptionor shown inthe accompanyingdrawings shall be interpreted as illustrative an not in a limitingsense. Y

What is claimed is:

1. In a system for correcting for' deviation ef` fects of a magneticcompass, the combination Vwith an intermittently operabledeviation-causeV ing apparatus and a magnetic compass mounted insubjective relation thereto, of a plurality jof relatively angularlydisposed coils mounted in cooperable relation to said compass, means forproviding a continuous and controlled energization of said coils tothereby provide a magnetic ileld of a nrst predetermined intensity anddirection to compensate the compass for local'xed deviation-causingeffects, `means for additionally controlling the current flowrespectively in all of said coils to subject said compass to a eid of asecond xed and predetermined value in magnitude and directionsubstantially equal and with an intermittently operable deviationcausingapparatus and a magnetic compass mounted in subjective relation thereto,of means comprising three coils having their axes arranged in mutuallyperpendicular relationship and in cooperable relation to said compass.means for providing a continuous and controlled energization of saidcoils to thereby provide, a magnetic ileld of a ilrstpredeterminedintensity and direction to compensate the compass for localfixed deviation-causing efiects, means for additionally controlling thecurrent ow respectively in all of said coils to subject said compass'toa eld of a second fixed and predetermined value in magnitude anddirection substantially equal and opposite to the combined magneticeil'ect of said apparatus and the local relatively anguiarly disposedcoils mounted in cooperable relation to said compass, means forproviding a continuous and controlled energization of said coils tothereby provide a magnetic iield of a iirst predetermined intensity anddi rection to compensate the compass for local xed deviation-causingeii'ects, means for additionally controlling the current iiowrespectively in all of said coils to subject said compass to a ileid ofa second fixed and predetermined value in magnitude and directionsubstantially equal and opposite to the combined magnetic effect of saidapparatus andthe local fixed deviation-causing effects on said compass,and a common means for controlling the operation of said apparatus andthe operation of said means for additionally controlling the current owrespectively in all of the coils whereby simultaneously to change thevalue of the magnetic iield developed by said coils from one value toanother when said apparatus is turned on and off.

FREDERICK D. BRADDON.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS VNumber Name Date 41,839 Gisborne et al. Mar. 3,1864 1,596,639 Vion Aug. 17, 1926 1,892,826 Bettison et al. Jan. 3, 19332,053,154 La Pierre Sept. 1, 1936 2,300,404 Carter et al Nov. 3, 19422,324,718 Noxon July 201943 FOREIGN PATENTS Number UCountry Date 13,752"Great Britain 1896 356,844 Germany 1922 666,594 Germany 1938 OTHERREFERENCES Knotts Catalog of Scientific Instruments (1921).

